In recent years, in a mobile terminal (for example, a smart phone) that allows a wireless communication, the demand for transmission and reception of a large amount of content is increased. For example, wireless communication in a millimeter wave band having a transmission rate of 1 Gbps or greater, particularly, in a 60 GHz band has attracted attention. As the semiconductor technology has advanced in recent years, it is expected that the wireless communication using the millimeter wave band becomes possible.
A quadrature hybrid coupler is used as one of circuit components used in the wireless communication in the millimeter wave band. The quadrature hybrid coupler is a circuit component of one input and two outputs, for example, and ideally, two output signals have the same amplitude and a phase difference of 90 degrees therebetween. In the wireless communication in the millimeter wave band, the quadrature hybrid coupler is built in an integrated circuit (IC) of a wireless communication terminal.
FIG. 19 is a diagram illustrating a quadrature hybrid coupler disclosed in Patent Literature 1. FIG. 19(a) is an equivalent circuit diagram, and FIG. 19(b) is a layout diagram. The quadrature hybrid coupler in Patent Literature 1 is a quadrature hybrid coupler of a modified capacitive coupling type. Parasitic capacitance between spiral inductors L3 and L4 is used for the coupling capacitor.
FIG. 20 is a layout diagram of a quadrature hybrid coupler disclosed in Non-Patent Literature 1. In FIG. 20, a quadrature hybrid coupler of a magnetic coupling type is shown, in which a transformer is disposed at the center thereof, and a coupling capacitor and a shunt capacitor are disposed on opposite sides thereof.
An equivalent circuit diagram and a layout example of a hybrid coupler are disclosed in Patent Literature 2. The hybrid coupler disclosed in Patent Literature 2 is a quadrature hybrid coupler of a wavelength-reduced magnetic coupling type. Parasitic capacitance between transformers is used as a coupling capacitor and a shunt capacitor.
Patent Literature 3, Patent Literature 4 and Patent Literature 5 disclose circuits of the similar hybrid coupler. The circuits will be appropriately referenced in description of embodiments of the present disclosure, and description thereof will be omitted herein.